With regard to industrial products such as vehicles, the color is significant in terms of the marketability. Generally, during the process of developing and designing industrial products such as vehicles, colors are designed based on the function and concept of the products.
When coloring is done by applying paint, colors obtained by application are called “paint colors”. Usually, when designing colors, a color designer of a product (hereinafter referred to as a “user”) tells a paint manufacturer the texture desired for a paint color, and asks the paint manufacturer to develop the paint color accordingly. The “texture” of a paint color denotes the impression received by an observer when looking at the paint color, as well as the impression given by the paint color. The paint manufacturer's engineer designs a paint color in view of the texture desired by the user. The user evaluates the paint color designed by the paint manufacturer, and may request that the paint color be modified such that the paint color matches the desired texture; the paint manufacturer's engineer then redesigns the paint color according to the request. Such a cycle is repeated between the user and the paint manufacturer's engineer to complete the paint color desired by the user.
During the first stage of the paint color design cycle described above, the paint manufacturer's engineer understands the texture that the user desires for the paint color, then searches for a paint color that matches the texture desired by the user among numerous paint colors that have been designed (hereinafter referred to as stock colors), and then presents the paint color obtained through the search to the user for evaluation. At this time, if the paint color presented to the user by the paint manufacturer is greatly different from the texture desired by the user, the design process of the paint color must be started over from the first stage of the above-described cycle, resulting in a large number of industrial steps required for designing a paint color.
Usually, when designing a paint color, the texture desired by the user is conveyed to the paint manufacturer's engineer by terms expressing textures such as translucent appearance, deepness appearance, three-dimensional appearance, etc. (hereinafter these words are referred to as “impression terms”). However, because the impression that one receives from these impression terms varies depending on the individual, the texture desired by the user is often not accurately conveyed to the paint manufacturer's engineer.
There have been attempts to quantify the textures expressed by the impression terms. For example, Patent Document 1 below discloses a method of quantifying the textures of metallic paint colors, such as metallic appearance, clearness appearance, etc., based on evaluation values obtained from colorimetric values of the paint colors using a specific function.    Patent Document 1: Japanese Unexamined Patent Publication No. 2003-279413    Patent Document 2: Japanese Unexamined Patent Publication No. H11-211569    Non-Patent Document 1: Touru HIRAYAMA, Shin YAMANAGA, Shinichi GAMOU, “Visual Evaluation and Digital Image Analysis of Micro-brilliance (II)”, Research on Coatings, Kansai Paint Co., Ltd., No. 138, July 2002    Non-Patent Document 2: Eiji NOMURA, Touru HIRAYAMA “Visual Evaluation and Digital Image Analysis of Micro-brilliance”, Research on Coatings, Kansai Paint Co., Ltd., No. 132, April 1999